Ink, and ink-jet recording method and apparatus employing the ink

ABSTRACT

Provided is an ink containing a recording agent and a liquid medium for dissolution or dispersion thereof, said ink comprising, as the recording agent, a compound represented by the general formula (A) ##STR1## where n is 0 or 1; R 1 , R 2 , and R 3  are respectively a substituent selected from the group consisting of hydrogen, methyl, methoxy, hydroxy, amino, acetylamino, and sulfonic acid; and M is an alkali metal, ammonium, or an organic ammonium.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink, an ink-jet recording methodemploying the ink, and an apparatus employing the ink. Moreparticularly, the present invention relates to a recording liquid whichgives high density and water resistance of printed letters on non-coatedpaper such as wood-free paper, paper for copying, bond paper, paper forreporting, and the like, and which gives improved indoor discolorationof an image recorded on coated paper having an image-receiving layerthereon composed of a binder and a pigment. The present invention alsorelates to an ink-jet recording method, an ink-jet recording unit, anink-jet recording apparatus, and an ink cartridge.

2. Related Background Art

Heretofore, aqueous inks having a water-soluble dye dissolved in anaqueous medium have been used for ink-jet recording. The inks for such ause are required to have the properties as below:

(1) giving sufficient density of images,

(2) having satisfactory drying property on recording mediums,

(3) causing little feathering or running of images,

(4) causing no flowing-out of the recorded images when brought intocontact with water, alcohol, or the like, or allowing satisfactorydecipherment even when some flowing out occurs (water-resistance),

(5) giving high light-fastness of recorded images,

(6) causing no clogging of a tip of a pen or a nozzle,

(7) causing no inconvenience in printed images such as blurring andscratching in continuous recording or at the re-start of recording aftera long term of intermission of the recording (ejection stability),

(8) being stable during storage,

(9) causing no problem on contact with a constituting member of arecording means on use,

(10) giving no hazard to an operator,

and so forth. Furthermore, in an ink-jet recording system, utilizingthermal energy, the property below is required in addition to the aboverequirements:

(11) having high heat resistance, and giving no adverse influence to athermal energy-generating means.

As a specific example of the dye, C.I. Food Black 2 is mainly used inink-jet recording for both mono-color and full-color images (seeJapanese Patent Application Laid-open No. 59-93766, and No. 59-93768).

An ink using C.I. Food Black 2 is satisfactory in density of recordedimages, but still involves problems on light-fastness andwater-resistance of recorded images: the black color turns brown onprolonged light exposure or on posting-up of printed matters inproximity to a copying machine, resulting in remarkable deterioration ofthe image quality, and difficulty in decipherment in test ofwater-spilling.

An ink is disclosed which has ejection stability, water resistance ofimages, and other properties improved by introducing at least onespecific structural unit into a dye structure in Japanese PatentApplication Laid-open No. 1-135880. Further, a recording liquid of blackcolor is disclosed, in Japanese Patent Application Laid-open No.1-193375, which has high affinity to recording media, and is superior infixability and water-resistance, giving satisfactory quality of printedletters on an ordinary paper. Furthermore, a recording liquid isdisclosed which is improved in ejection stability, and light fastness ofimages in Japanese Patent Publication No. 62-010274.

The ink is required firstly to have suitability for an employedrecording system, and secondly is required to give satisfactoryproperties of printed matters such as quality and fastness of theimages. However, it is considerably difficult to satisfy simultaneouslyall of the aforementioned various requirements on performances, asunderstood from the prior art disclosures cited above.

The quality of the printed letters mostly depends on a liquid medium ofthe ink, although it depends secondarily on properties of the dyeitself.

The fastness of the printed matter is directly influenced by the dyeproperties. In particular, light-fastness is the most important of thefastnesses, and improvement of the light-fastness has been tried asdescribed above.

Another problem, which has not been noticed but has come to be noticedas a consequence of technical progress, is discoloration or colorchange. The discoloration is especially serious in black ink which isused in a large quantity. In full color images, the image qualitydeteriorates rapidly by the discoloration.

The discoloration proceeds indoors also without direct sunlightillumination. The discoloration further depends on the kind of arecording medium for forming images thereon, being remarkable on papercontaining silica or the like as a pigment. The widely used C.I. FoodBlack 2 is not free from this problem.

Dyes having satisfactory light-fastness have been sought in order tocancel the disadvantage of C.I. Food Black 2. Consequently, dyes arefound which are satisfactory for use on ordinary paper. However, the inkcausing less problems on ordinary paper discolors significantly oncoated paper which has an ink-receiving layer formed on a substrate andcontaining a pigment and a binder for the purpose of improving imagequality such as color-developing property of the dyes, sharpness, andresolution. Thus the problem is not solved by merely employing alight-fast dye.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a black ink which hasthe above generally required properties and gives no discoloration ofthe image even on coated paper.

Another object of the present invention is to provide an ink-jetrecording method and an apparatus employing the ink.

According to an aspect of the present invention, there is provided anink containing a recording agent and a liquid medium for dissolution ordispersion thereof, the ink comprising, as the recording agent, acompound represented by the general formula (A) ##STR2## where n is 0 or1; R₁, R₂, and R₃ are respectively a substituent selected from the groupconsisting of hydrogen, methyl, methoxy, hydroxy, amino, acetylamino,and sulfonic acid; and M is an alkali metal, ammonium, or an organicammonium.

According to another aspect of the present invention, there is providedan ink-jet recording method for recording on a recording medium withdroplets of ink, the ink being a liquid composition containing at leastone compound represented by the general formula (A) above.

According to still another aspect of the present invention, there isprovided a recording unit having an ink container portion for holding anink and a head portion for ejecting the ink in droplets, the ink being aliquid composition containing at least one compound represented by thegeneral formula (A) above.

According to a further aspect of the present invention, there isprovided an ink cartridge having an ink container portion for holding anink, the ink being a liquid composition containing at least one compoundrepresented by the general formula (A) above.

According to a still further aspect of the present invention, there isprovided an ink-jet recording apparatus having a recording unitdescribed above.

According to a still further aspect of the present invention, there isprovided a method for using the ink described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A, and FIG. 1B are respectively a longitudinal cross-sectionalview and a lateral cross-sectional view of a head portion of an ink-jetrecording apparatus.

FIG. 2 is an oblique view of a multiplicate form of the head of FIG. 1.

FIG. 3 is an oblique view of an ink-jet recording apparatus.

FIG. 4 is a longitudinal cross-sectional view of an ink cartridge.

FIG. 5 is an oblique view of a recording unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The ink of the present invention comprises a compound represented by thegeneral formula (A) below: ##STR3## where n is 0 or 1; R₁, R₂, and R₃are respectively a substituent selected from the group consisting ofhydrogen, methyl, methoxy, hydroxy, amino, acetylamino, and sulfonicacid; and M is an alkali metal, ammonium, or an organic ammonium.

According to the present invention, use of the above-described compoundas the coloring matter for an ink provides an ink which gives lessindoor discoloration of image even on coated paper.

Preferred embodiments of the present invention are described to explainthe present invention in more detail.

The specific examples of the compounds (or dyes) represented by thegeneral formula (A) above which mainly characterize the presentinvention include: ##STR4##

Among the dyes above, more preferable are those in which the azo groupsare bonded to 2- and 7-positions of the naphthalene ring.

The dyes used in the present invention are generally sodium salts ofcompounds having water-soluble groups such as a sulfonic acid group. Thedyes, however, are not limited to sodium salts, but include dyes havingother counter ions such as potassium, lithium, ammonium, organic aminesor the like, which are effective similarly.

The above dyes are synthesized according to a conventional manner suchas described in "Theory and Production in Dye Chemistry" by YutakaHosoda, as below.

SYNTHESIS EXAMPLE

The exemplified Dye No. 2 is synthesized as follows.

3'-amino-4'-methoxyacetanilide is diazotized in a conventional manner,and is coupled with 2,5-dimethoxyaniline. The product is furtherdiazotized by sodium nitrite and coupled with 2R acid. Still further,the product is diazotized by sodium nitrite and is added to a solutionof m-phenylenediamine-4-sulfonic acid to be coupled at a range of from 4to 5. The resulting dye is salted out by addition of sodium chloride andis collected by filtration. Impurities are eliminated from the productby repetition of dissolution in water, salting-out by sodium chloride,and collection by filtration. Thereafter, the product is purified bymeans of ultrafiltration apparatus (made by Sartorius GmbH). Thus theexemplified Dye No. 2 is synthesized.

The amount of the aforementioned dye to be used in the ink of thepresent invention is generally within the range of from 0.1 to 15% byweight, preferably 0.5 to 10% by weight, still more preferably from 0.5to 6% by weight of the total weight of the ink, although the amount isnot specially limited thereto.

A suitable aqueous medium for the ink of the present invention is wateror a mixed solvent composed of water and a water-soluble organicsolvent.

The water to be used is preferably deionized water, and not ordinarywater containing various ions.

Suitable water-soluble organic solvents to be mixed with water includealcohols having 1 to 5 carbons such as methyl alcohol, ethyl alcohol,n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol,tert-butyl alcohol, isobutyl alcohol, n-pentanol, etc.; amides such asdimethylformamide, dimethylacetamide, etc.; ketones and ketoalcoholssuch as acetone, diacetone alcohol, etc.; cyclic ethers such as dioxane,etc.; polyalkylene glycols such as polyethylene glycol, polypropyleneglycol, etc.; alkylene glycols having an alkylene group of 2 to 6carbons such as ethylene glycol, propylene glycol, butylene glycol,triethylene glycol, 1,2,6-hexane triol, thiodiglycol, hexylene glycol,diethylene glycol, etc.; glycerin; lower alkyl ethers of a polyhydricalcohol such as ethylene glycol monomethyl (or monoethyl) ether,diethylene glycol monomethyl (or monoethyl) ether, triethylene glycolmonomethyl (or monoethyl) ether, etc.; lower alkyl diethers of apolyhydric alcohol such as triethylene glycol dimethyl (or diethyl)ether, tetraethylene glycol dimethyl (or diethyl) ether, etc.;sulfolane, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, andthe like.

A suitable organic solvent is selected and used from the above solventsand the like. In particular, glycerin or a polyethylene oxide of apolymerization degree of 3 to 6 is preferable for prevention of cloggingwith ink; a nitrogen-containing cyclic compound or an ether compound ofa polyalkylene oxide is preferable in view of image density and inkejection stability; and use of a lower alkyl alcohol or a surfactant ispreferable in view of frequency responsiveness. Accordingly, thepreferable composition of the solvent in the present invention containsa main component as above in addition to water.

The content of the above water-soluble organic solvent in the ink isgenerally in the range of from 2 to 80% by weight, preferably from 3 to70% by weight, still more preferably from 4 to 60% by weight of thetotal weight of the ink.

The amount of water to be used is generally in the range of from 10 to97.5% by weight, preferably not less than 35% by weight, still morepreferably not less than 45% by weight of the total weight of the ink.At a less amount of the water, a low-volatile organic solvent remains ina formed image, which undesirably causes problems of migration of thedye and running or feathering of the formed image.

The ink of the present invention may optionally contain a pH-adjustingagent, a viscosity-adjusting agent, a surface tension-adjusting agent,or the like in addition to the components described above. ThepH-adjusting agent includes amines such as diethanolamine,triethanolamine, etc.; inorganic alkali salts including hydroxides suchas sodium hydroxide, lithium hydroxide, potassium hydroxide, etc.;organic acid salts such as lithium acetate, etc.; organic acids, mineralacids, and the like.

The ink of the present invention desirably has properties of a viscosityat 25° C. within the range of from 1 to 20 cps, preferably from 1 to 15cps; a surface tension of not less than 30 dyn/cm, preferably not lessthan 40 dyn/cm; and pH within the range of from 4 to 10.

As the recording method for the ink of the present invention, effectiveis an ink-jet recording system. As the recording medium therefor, coatedpaper is effective to obtain an image with high sharpness and highresolution.

The recording medium used in the present invention may be of any mediaincluding general-purpose ordinary paper (e.g., wood-free paper,medium-quality paper, and bond paper), coated paper, plastic OHP films,and the like. In particular, use of coated paper will achieveconsiderable effects. The coated paper, which is generally constructedfrom wood-free paper as the base material and an ink-receiving layerformed thereon composed of a pigment and a binder, includes in thepresent invention such paper having an ink receiving layer in whichpaper fibers of the base material exist mixedly in the ink-receivinglayer.

The ink of the present invention is especially suitable for an ink-jetrecording method, which is a type of ejecting ink upon utilizing thefoaming phenomenon of ink caused by thermal energy, because the ink hasthe characteristics of extremely high stability of ink ejection andnon-occurrence of a satellite dot. For this use, thermal properties ofthe ink is sometimes adjusted (e.g., specific heat, thermal expansioncoefficient, thermal conductivity, etc.).

The ink of the present invention, which is employed particularlysuitably for an ink-jet recording method for recording by ejecting inkdroplets by thermal energy, is naturally useful also for general writingutensils.

The methods and the apparatus suitable for the use of the ink of thepresent invention are those which provide thermal energy to ink in acell in a recording head in correspondence with recording signals toform liquid droplets by the thermal energy.

An example of the constitution of the heads, which is a main portion ofthe apparatus, is shown in FIG. 1A, FIG. 1B, and FIG. 2.

A head 13 is formed by bonding a plate of glass, ceramics, or plasticshaving a groove 14 with a heat-generating head 15. (The type of the headis not limited to the one shown in the figure.) The heat-generating head15 is constituted of a protection layer 16 formed of silicon oxide orthe like, aluminum electrodes 17-1 and 17-2, a heat-generatingresistance layer 18 formed of nichrome or the like, a heat accumulationlayer 19, and a substrate plate 20 having a good heat-releasing propertymade of alumina or the like.

Ink 21 reaches the ejection orifice 22 (a fine pore), forming a meniscusby action of pressure P not shown in the figure.

On application of an electric signal to the electrodes 17-1 and 17-2,the region designated by a symbol "n" on the heat-generation head 15generates heat abruptly to form a bubble in the ink 21 at the positionadjacent thereto. The pressure generated by the bubble pushes out themeniscus 23 and ejects the ink 21, as recording droplets 24, and the inkdroplets fly to a recording medium 25. FIG. 2 illustrates an appearanceof a multi-head constructed by juxtaposing a multiplicity of heads shownin FIG. 1A. The multi-head is prepared by bonding a glass plate havingmulti-grooves with a heat-generation head 28 similar to the onedescribed in FIG. 1A.

Incidentally, FIG. 1A is a cross-sectional view of the head 13 along anink flow path, and FIG. 1B is a cross-sectional view of the head at theline A-B in FIG. 1A.

FIG. 3 illustrates an example of the ink-jet recording apparatus havingsuch a head mounted therein.

In FIG. 3, a blade 61 as a wiping member is held at one end by ablade-holding member. The blade 61 is placed at a position adjacent tothe recording region of the recording head, and in this example, is heldin protrusion into the moving path of the recording head. A cap 62 isplaced at a home position adjacent to the blade 61, and is constitutedsuch that it moves in the direction perpendicular to the movingdirection of the recording head to come into contact with the ejectionnozzle face to cap the nozzles. An ink absorption member 63 is providedat a position adjacent to the blade 61, and is held in protrusion intothe moving path of the recording head in a manner similar to that of theblade 61. The aforementioned blade 61, the cap 62 and the absorptionmember 63 constitute an ejection-recovery portion 64, and the blade 61and the absorption member 63 remove water, dust, and the like from theink ejecting nozzle face.

A recording head 65 has an ejection energy generation means forejection, and conducts recording by ejecting ink toward a recordingmedium opposing the ejection nozzle face. A carriage 66 is provided forsupporting and moving the recording head 65. The carriage 66 is engagedslidably with a guide rod 67. A portion of the carriage 66 is connected(not shown in the figure) to a belt 69 driven by a motor 68, so that thecarriage 66 is movable along the guide rod 67 to the recording region ofthe recording head and an adjacent region thereto.

The constitution of a paper delivery portion 51 for delivery of arecording medium and a paper delivery roller 52 driven by a motor (notshown in the figure) delivers the recording medium to the positionopposing to the ejecting nozzle face of the recording head, and therecording medium is discharged with the progress of the recording topaper discharge portion provided with paper-discharge rollers 53.

In the above constitution, the cap 62 of the ejection-recovery portion64 is out of the moving path of the recording head 65, while the blade61 is protruded toward the moving path. Therefore, the ejecting nozzleface of the recording head 65 is wiped therewith. The cap 62 moves toprotrude toward the moving path of the recording head when the cap 62comes into contact for capping with the ejecting nozzle face of therecording head.

At the time when the recording head moves from the home position to therecord-starting position, the cap 62 and the blade 61 are at the sameposition as in the above-mentioned wiping time, so that the ejectionnozzle face of the recording head is wiped also in this movement.

The recording head moves to the home position not only at the end of therecording and at the time of ejection recovery, but also at apredetermined interval during movement for recording in the recordingregion. By such movement, the wiping is conducted.

FIG. 4 illustrates an example of the ink cartridge 45 containing ink tobe supplied through an ink supplying member such as a tube (not shown).The ink container portion 40, for example an ink bag, contains an ink tobe supplied, and has a rubber plug 42 at the tip. By inserting a needle(not shown in the figure) into the plug 42, the ink in the ink containerportion 40 is made suppliable. An absorption member 44 absorbs wasteink.

The ink container portion has preferably a liquid-contacting face madeof polyolefin, especially polyethylene in the present invention.

The ink-jet recording apparatus used in the present invention is notlimited to the above-mentioned one which has separately a head and anink cartridge, but integration thereof as shown in FIG. 5 may suitablybe used.

In FIG. 5, a recording unit 70 houses an ink container portion such asan ink absorption member, and the ink in the ink absorption member isejected from a head 71 having a plurality of orifices. The material forthe ink absorption member is preferably polyurethane in the presentinvention.

Air-communication opening 72 is provided to communicate interior of thecartridge with the open air.

The recording unit 70 may be used in place of the recording head shownin FIG. 3, and is readily mountable to and demountable from the carriage66.

The present invention is described in more detail referring to examplesand comparative examples. The term "part" in the description is base onweight unless otherwise mentioned.

EXAMPLES (1) Preparation of Ink

The components shown in Table 1 below were mixed and dissolved. Themixture was filtered through a filter having a pore diameter of 0.45 μmto provide a plurality of kinds of ink of the present invention as shownin Table 1.

                  TABLE 1                                                         ______________________________________                                                                    Quantity                                          No.     Ink components      used                                              ______________________________________                                        1       Exemplified dye No. 1                                                                              3 parts                                                  Diethylene glycol   25 parts                                                  Pure water          72 parts                                          2       Exemplified dye No. 2                                                                              3 parts                                                  Diethylene glycol   20 parts                                                  N-methyl-2-pyrrolidone                                                                            15 parts                                                  Pure water          62 parts                                          3       Exemplified dye No. 3                                                                              3 parts                                                  Polyethylene glycol 300                                                                           20 parts                                                  Pure water          77 parts                                          4       Exemplified dye No. 4                                                                              3 parts                                                  Ethylene glycol     25 parts                                                  Pure water          72 parts                                          5       Exemplified dye No. 5                                                                              3 parts                                                  Glycerin            15 parts                                                  Pure water          82 parts                                          6       Exemplified dye No. 6                                                                              3 parts                                                  Diethylene glycol   15 parts                                                  Ethylene glycol monoethyl ether                                                                   10 parts                                                  Pure water          72 parts                                          7       Exemplified dye No. 7                                                                              3 parts                                                  Ethylene glycol     20 parts                                                  Isopropyl alcohol    5 parts                                                  Pure water          72 parts                                          8       Exemplified dye No. 8                                                                              3 parts                                                  Glycerin            15 parts                                                  N-methyl-2-pyrrolidone                                                                            10 parts                                                  Pure water          72 parts                                          9       Exemplified dye No. 9                                                                              3 parts                                                  Ethylene glycol     20 parts                                                  Ethanol              5 parts                                                  Pure water          72 parts                                          10      Exemplified dye No. 10                                                                             3 parts                                                  Diethylene glycol   25 parts                                                  Pure water          72 parts                                          11      Exemplified dye No. 11                                                                             3 parts                                                  Polyethylene glycol 300                                                                           20 parts                                                  Isopropyl alcohol   10 parts                                                  Pure water          67 parts                                          12      Exemplified dye No. 12                                                                             3 parts                                                  Diethylene glycol   20 parts                                                  n-Propyl alcohol     5 parts                                                  Pure water          72 parts                                          ______________________________________                                    

(2) Application examples

The inks shown in Table 1 above were respectively mounted on an ink-jetprinter BJ-80A (made by Canon K.K., nozzle size: 50×40 μm, 24 nozzles)employing a heat-generating element as an ink-ejecting energy source.Printing was conducted on the recording mediums shown below forevaluation regarding the items of (a) clogging on re-start of printingafter a short intermission of printing, (b) recoverability from cloggingon re-start of printing after a long term of intermission of printing,and (c) resistance of printed image to discoloration.

Recording medium A: Coated paper NM for ink-jet (trade name, made byMitsubishi Paper Mills, Ltd.)

Recording medium B: Coated paper FC-3 for ink-jet (trade name, made byJujo Paper Mfg. Co., Ltd.)

Recording medium C: Coated paper IJ Mat Coat M for ink-jet (trade name,made by Mitsubishi Paper Mills, Ltd.)

Recording medium D: Copying paper, Canon Paper Dry (trade name made byCanon Sales Co., Inc.)

(3) Method and Results of Evaluation

(a) Clogging on re-start of printing after a short intermission ofprinting

Alphabetical and numeral letters were printed continuously for 10minutes on the Recording medium C by employing the ink filled in theprinter. Then the printer was left standing without capping for 10minutes under the conditions of 20° C.±5° C. and 50±10% RH. Thereafteralphabetical and numeral letters were again printed, and the presence orabsence of defects such as blurring and chipping of printed letters wasexamined. As the result, no defect was observed.

(b) Recoverability from clogging after a long term of intermission ofprinting

Alphabetical and numeral letters were printed continuously for 10minutes on the Recording medium C by employing the ink filled in theprinter. Then the printer was left standing without capping for 7 daysunder the conditions of 60° C. and 10±5% RH. Thereafter operation forrecovery from nozzle clogging was conducted, and the repetition times ofthe recovery operation was counted which is required to conduct normalprinting without defects such as blurring and chipping of letters. Asthe result, repetition of the recovery operation of from one to fivetimes of the recovery operation was enough for normal printing.

(c) Resistance to discoloration

Solid printing was conducted on the recording mediums A, B, C, and D ina size of 10 mm×30 mm. The printed recording mediums were left standingfor 30 minutes in a dark chamber containing ozone at a concentration of0.3±0.05% by volume for accelerating discoloration. The color difference(ΔE^(*) ab) caused by the 30 minute standing was measured (according toJIS Z8730). The results are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                   ΔE*ab                                                                   Recording medium                                                   Ink No.      A     B           C   D                                          ______________________________________                                        1            4.2   3.6         5.1 2.7                                        2            5.5   4.8         5.2 3.0                                        3            4.9   4.2         4.5 2.9                                        4            4.8   5.0         4.1 3.1                                        5            5.1   4.9         4.2 3.3                                        6            6.0   5.9         4.6 4.0                                        7            5.2   5.0         4.7 4.1                                        8            5.4   4.0         3.9 3.7                                        9            6.1   5.5         5.6 4.2                                        10           5.6   5.6         4.8 3.0                                        11           5.1   4.5         4.2 3.4                                        12           6.1   5.9         5.2 3.9                                        ______________________________________                                    

The color difference of any of the printed matters caused by exposure toindoor light for three months was not more than 3.

COMPARATIVE EXAMPLES

The inks shown in Table 3 below were prepared by mixing the componentsin Table 3 and treating them in the same manner as in the Examples. Eachink was employed for solid printing on the recording mediums A, B, and Cby means of the same recording apparatus as in Examples. The testspecimens of the printed matters were subjected to the test in theaforementioned ozone-containing test chamber in the same manner asabove. As the results, all of the values ΔE^(*) ab were not less than20. The color differences after exposure to indoor light for threemonths were not less than 12 for all of the samples.

                  TABLE 3                                                         ______________________________________                                                                     Quantity                                         No.     Ink components       used                                             ______________________________________                                        13      Undermentioned dye 13                                                                               3 parts                                                 Diethylene glycol    25 parts                                                 Pure water           72 parts                                         14      Undermentioned dye 14                                                                               3 parts                                                 Ethylene glycol      20 parts                                                 Polyethylene glycol 300                                                                            10 parts                                                 Pure water           67 parts                                         15      Undermentioned dye No. 15                                                                           3 parts                                                 Glycerin             15 parts                                                 Diethylene glycol monoethyl ether                                                                  10 parts                                                 Pure water           72 parts                                         16      Undermentioned dye No. 16                                                                           3 parts                                                 Diethylene glycol    20 parts                                                 Isopropyl alcohol     5 parts                                                 Pure water           72 parts                                         17      Undermentioned dye No. 17                                                                           3 parts                                                 Ethylene glycol      20 parts                                                 N-methyl-2-pyrrolidone                                                                             10 parts                                                 Pure water           67 parts                                         ______________________________________                                         ##STR5##

In the present invention, the use of the compound (or dye) representedby the general formula (A) as the dye in an ink gives a recording liquidwhich has the properties required for printed matters on ordinary paperand forms images of less discoloration on coated paper. Further the usethereof gives an image of high image quality, exhibiting high resolutionand less discoloration, and having satisfactory fastness properties.

The ink of the present invention exhibits the aforementionedcharacteristics sufficiently at the neutral range of pH 4 to 10, whichis satisfactory in view of safety because of no need of addition forstrongly alkaline substances as described in Japanese Patent ApplicationLaid-open No. 56-57862.

Furthermore, the ink of the present invention, even when applied toink-jet recording method which ejects ink by action of thermal energy,can be used stably for long time without forming an adhering matter onthe heater, and does not change its physical properties or forming nosolid deposit during storage.

What is claimed is:
 1. An ink containing a recording agent and a liquidmedium for dissolution or dispersion thereof, said ink comprising, asthe recording agent, a compound represented by the general formula (A)##STR6## where n is 0 or 1; R₁, R₂, and R₃ are respectively asubstituent selected from the group consisting of hydrogen, methyl,methoxy, hydroxy, amino, acetylamino, and sulfonic acid; and M is analkali metal, ammonium, or an organic ammonium.
 2. The ink of claim 1,wherein the compound represented by the general formula (A) is at leastone selected from the following compounds of from No. 1 to No. 12:##STR7##
 3. The ink of claim 1, wherein pH of the ink is within therange of from 4 to
 10. 4. The ink of claim 1, wherein said recordingagent is contained in an amount within the range of from 0.1 to 15% byweight of the total weight of the ink.
 5. The ink of claim 1, whereinthe liquid medium comprises a mixed solvent of water and a water-solubleorganic solvent.
 6. The ink of claim 5, wherein the water is containedin an amount within the range of from 10 to 97.5% by weight of the totalweight of the ink.
 7. The ink of claim 5, wherein the water-solubleorganic solvent is contained in an amount within the range of from 2 to80% by weight of the total weight of the ink.
 8. In an ink-jet recordingmethod for recording on a recording medium with droplets of ink, theimprovement comprising employing a liquid ink composition containing atleast one compound represented by the general formula (A) ##STR8## wheren is 0 or 1; R₁, R₂, and R₃ are respectively a substituent selected fromthe group consisting of hydrogen, methyl, methoxy, hydroxy, amino,acetylamino, and sulfonic acid; and M is an alkali metal, ammonium, oran organic ammonium.
 9. In the ink-jet recording method of claim 8,wherein the compound represented by the general formula (A) is at leastone selected from the following compounds of from No. 1 to No. 12:##STR9##
 10. In the ink-jet recording method of claim 8, wherein pH ofthe ink is within the range of from 4 to
 10. 11. In the ink-jetrecording method of claim 8, wherein the compound represented by thegeneral formula (A) is contained in an amount within the range of from0.1 to 15% by weight of the total weight of the ink.
 12. In the ink-jetrecording method of claim 8, wherein the ink further comprises a mixedsolvent of water and a water-soluble organic solvent.
 13. In the ink-jetrecording method of claim 12, wherein the water is contained in anamount within the range of from 10 to 97.5% by weight of the totalweight of the ink.
 14. In the ink-jet recording method of claim 12,wherein the water-soluble organic solvent is contained in an amountwithin the range of from 2 to 80% of the total weight of the ink.
 15. Inthe ink-jet recording method of claim 8, wherein the recording medium isnon-coated paper or coated paper.
 16. In the ink-jet recording method ofclaim 8, wherein the ink is ejected by action of thermal energy on theink.
 17. A recording unit having an ink container portion for holding anink and a head for ejecting the ink in droplets, said ink being a liquidcomposition containing at least one compound represented by the generalformula (A) ##STR10## where n is 0 or 1; R₁, R₂, and R₃ are respectivelya substituent selected from the group consisting of hydrogen, methyl,methoxy, hydroxy, amino, acetylamino, and sulfonic acid; and M is analkali metal, ammonium, or an organic ammonium.
 18. The recording unitof claim 17, wherein the compound represented by the general formula (A)is at least one selected from the following compounds of from No. 1 toNo. 12: ##STR11##
 19. The recording unit of claim 17, wherein pH of theink is within the range of from 4 to
 10. 20. The recording unit of claim17, wherein the compound represented by the general formula (A) iscontained in an amount within the range of from 0.1 to 15% by weight ofthe total weight of the ink.
 21. The recording unit of claim 17, whereinthe ink further comprises a mixed solvent of water and a water-solubleorganic solvent.
 22. The recording unit of claim 21, wherein the wateris contained in an amount within the range of from 10 to 97.5% by weightof the total weight of the ink.
 23. The recording unit of claim 21,wherein the water-soluble organic solvent is contained in an amountwithin the range of from 2 to 80% of the total weight of the ink. 24.The recording unit of claim 17, wherein the head ejects ink droplets byaction of thermal energy on the ink.
 25. The recording unit of claim 17,wherein the ink container portion comprises an ink absorption member.26. The recording unit of claim 25, wherein the ink absorption member isformed from polyurethane.
 27. An ink cartridge having an ink containerportion for holding an ink, said ink being a liquid compositioncontaining at least one compound represented by the general formula (A)##STR12## where n is 0 or 1; R₁, R₂, and R₃ are respectively asubstituent selected from the group consisting of hydrogen, methyl,methoxy, hydroxy, amino, acetylamino, and sulfonic acid; and M is analkali metal, ammonium, or an organic ammonium.
 28. The ink cartridge ofclaim 27, wherein the compound represented by the general formula (A) isat least one selected from the following compounds of from No. 1 to No.12: ##STR13##
 29. The ink cartridge of claim 27, wherein pH of the inkis within the range of from 4 to
 10. 30. The ink cartridge of claim 27,wherein the compound represented by the general formula (A) is containedin an amount within the range of from 0.1 to 15% by weight of the totalweight of the ink.
 31. The ink cartridge of claim 27, wherein the inkfurther comprises a mixed solvent of water and a water-soluble organicsolvent.
 32. The ink cartridge of claim 31, wherein the water iscontained in an amount within the range of from 10 to 97.5% by weight ofthe total weight of the ink.
 33. The ink cartridge of claim 31, whereinthe water-soluble organic solvent is contained in an amount within therange of from 2 to 80% of the total weight of the ink.
 34. The inkcartridge of claim 27, wherein the ink container portion is of a bagstructure.
 35. The ink cartridge of claim 27, wherein the ink containerportion has a liquid-contact face formed of polyolefin.